The present invention relates to the manufacture of textile yarns and relates, more particularly, to the production of yarns having the appearance of spun yarns but being formed from continuous polymer filaments.
At the outset it will be of use to explain briefly that the term "textured yarns" as employed herein embraces both "torque stretch yarns" and "set yarns". Torque stretch yarns are produced by subjecting yarns comprised of a bundle of filaments to a mechanical treatment to cause the yarns to assume a crimped or coiled configuration so that they have a certain inherent elasticity and have stretch characteristic which distinguish them from untreated yarns. These properties cause them to be highly desirable for certain applications such as stretch-to-fit garments where they have encountered a high degree of consumer acceptance. The most popular or highly used technique for producing torque stretch yarns is known as "false twist texturing". This procedure involves twisting a yarn about its own axis, heat setting the yarn, and then untwisting the yarn. As used herein "stretch yarn(s)" shall mean torque stretch yarn(s).
Closely related to torque stretch yarns are the "set yarns" and, here again, enormous commercial interest has been displayed in these set yarns in recent years. In brief, set yarn is stretch yarn which is created when a torque stretch yarn is relaxed from its fully stretched (straightened) configuration to the point where the crimped configuration is present in the yarn but the so-called pigtails caused by torque from the mechanical treatment of the yarn are not permitted to form. The yarn in this crimped configuration is then treated by heating and cooling so that a substantial amount of the torque is permanently removed from the yarn but the crimped is retained. Set yarns are of commercial importance because of their bulkiness and voluminosity and find wide use, for example, in knitted outerwear applications.
Spun yarn is produced by twisting together a plurality of staple length fibers. Yarns so spun have met with broad customer acceptance based upon appearance, softness of hand and covering power. With the advent of processes for the high rate production of synthetic polymer filaments many attempts have been made to treat these filaments to possess the characteristics of spun yarns. In the absence of some such processing the polymer filaments are smooth, flat and have what has been described as a "clammy" feel. Thus, such filaments have proven generally unacceptable, particularly in apparel applications.
Numerous techniques have evolved in the prior art endeavors to process continuous synthetic filaments so as to possess the characteristics of spun yarns. These include knit-de-knit crimping, stuffer-box crimping, gear crimping, edge crimping, and the aforementioned torque stretch technique. Much effort has been expended in developing yarns comprised of a plurality of the filaments having loose filamentary ends protruding from the yarn to simulate the staple fiber ends and thus the "hand" of a spun yarn and, for convenience, this is referred to herein as "stapilizing". Among these prior art stapilizing processes is a process which employs a rotating brush which rips and unravels the surface of a drawn filamentary yarn. Another process includes forming a yarn of filaments of different elongations, then drawing the yarn so as to break the lower elongation filaments while leaving the other filaments intact. the broken filaments provide loose ends intended to be akin to the loose ends of spun yarn. Other processes include subjecting the continuous filamentary yarn to an abrading action in its passage from a supply spool to a collecting package. Many of those methods have also been applied to the previously-described "textured" yarns. A recently patented process provides for modifying the torsional rigidity of the constituent filaments of the yarn so that at least some of the filaments will shear when false twisted to thus produce a stapilized yarn.